ESP32之OTA
技术经验 • dingxiao • 阅读数:3520 • 2019年10月14日 09:13
ESP32之OTA
0x01-OTA
OTA是Over the Air的缩写，顾名思义通过空中方式升级，所谓“空中”指的是远程无线方式，OTA可以理解为一种远程无线升级技术。在实际产品开发过程中，在线升级可以远程解决产品软件开发引入的问题，更好地满足用户需求。
0x02-ESP32的OTA升级方式
ESP32的OTA更新是使用 Wi-Fi 连接而不是串行端口将固件加载到 ESP 模块的过程。主要有三种方式可以实现OTA功能：
1）Arduino IDE：主要用于软件开发阶段，实现不接线固件烧写
2）Web Browser：通过 Web 浏览器手动提供应用程序更新模块
3）HTTP Server：自动使用http服务器 - 针对产品应用
其中以第3种方式作为产品级OTA方式更为方便可行。
0x03-OTA使用HTTP Server方式升级
参考网址：
https://blog.csdn.net/liwei16611/article/details/81051909
ESP32 连接 HTTP 服务器，发送请求 Get 升级固件；每次读取1KB固件数据，写入Flash。
ESP32 SPI Flash 内有与升级相关的（至少）四个分区：OTA data、Factory App、OTA_0、OTA_1。其中 FactoryApp 内存有出厂时的默认固件。
首次进行 OTA 升级时，OTA Demo 向 OTA_0 分区烧录目标固件，并在烧录完成后，更新 OTA data 分区数据并重启。
系统重启时获取 OTA data 分区数据进行计算，决定此后加载 OTA_0 分区的固件执行（而不是默认的 Factory App 分区内的固件），从而实现升级。
同理，若某次升级后 ESP32 已经在执行 OTA_0 内的固件，此时再升级时 OTA Demo 就会向 OTA_1 分区写入目标固件。再次启动后，执行 OTA_1 分区实现升级。以此类推，升级的目标固件始终在 OTA_0、OTA_1 两个分区之间交互烧录，不会影响到出厂时的 Factory App 固件。 
上图对应ESP32模块，可以方便的理解ESP32为什么配置了4MB的Flash空间。
0x04-参考代码
#include <WiFi.h>
#include <Update.h>
WiFiClient client;
// Variables to validate
// response from S3
int contentLength = 0;
bool isValidContentType = false;
// Your SSID and PSWD that the chip needs
// to connect to
const char* SSID = "YOUR-SSID";
const char* PSWD = "YOUR-SSID-PSWD";
// S3 Bucket Config
String host = "bucket-name.s3.ap-south-1.amazonaws.com"; // Host => bucket-name.s3.region.amazonaws.com
int port = 80; // Non https. For HTTPS 443. As of today, HTTPS doesn't work.
String bin = "/sketch-name.ino.bin"; // bin file name with a slash in front.
// Utility to extract header value from headers
String getHeaderValue(String header, String headerName) {
return header.substring(strlen(headerName.c_str()));
}
// OTA Logic
void execOTA() {
Serial.println("Connecting to: " + String(host));
// Connect to S3
if (client.connect(host.c_str(), port)) {
// Connection Succeed.
// Fecthing the bin
Serial.println("Fetching Bin: " + String(bin));
// Get the contents of the bin file
client.print(String("GET ") + bin + " HTTP/1.1\r\n" +
"Host: " + host + "\r\n" +
"Cache-Control: no-cache\r\n" +
"Connection: close\r\n\r\n");
// Check what is being sent
// Serial.print(String("GET ") + bin + " HTTP/1.1\r\n" +
// "Host: " + host + "\r\n" +
// "Cache-Control: no-cache\r\n" +
// "Connection: close\r\n\r\n");
unsigned long timeout = millis();
while (client.available() == 0) {
if (millis() - timeout > 5000) {
Serial.println("Client Timeout !");
client.stop();
return;
}
}
// Once the response is available,
// check stuff
/*
Response Structure
HTTP/1.1 200 OK
x-amz-id-2: NVKxnU1aIQMmpGKhSwpCBh8y2JPbak18QLIfE+OiUDOos+7UftZKjtCFqrwsGOZRN5Zee0jpTd0=
x-amz-request-id: 2D56B47560B764EC
Date: Wed, 14 Jun 2017 03:33:59 GMT
Last-Modified: Fri, 02 Jun 2017 14:50:11 GMT
ETag: "d2afebbaaebc38cd669ce36727152af9"
Accept-Ranges: bytes
Content-Type: application/octet-stream
Content-Length: 357280
Server: AmazonS3
{{BIN FILE CONTENTS}}
*/
while (client.available()) {
// read line till /n
String line = client.readStringUntil('\n');
// remove space, to check if the line is end of headers
line.trim();
// if the the line is empty,
// this is end of headers
// break the while and feed the
// remaining `client` to the
// Update.writeStream();
if (!line.length()) {
//headers ended
break; // and get the OTA started
}
// Check if the HTTP Response is 200
// else break and Exit Update
if (line.startsWith("HTTP/1.1")) {
if (line.indexOf("200") < 0) {
Serial.println("Got a non 200 status code from server. Exiting OTA Update.");
break;
}
}
// extract headers here
// Start with content length
if (line.startsWith("Content-Length: ")) {
contentLength = atoi((getHeaderValue(line, "Content-Length: ")).c_str());
Serial.println("Got " + String(contentLength) + " bytes from server");
}
// Next, the content type
if (line.startsWith("Content-Type: ")) {
String contentType = getHeaderValue(line, "Content-Type: ");
Serial.println("Got " + contentType + " payload.");
if (contentType == "application/octet-stream") {
isValidContentType = true;
}
}
}
} else {
// Connect to S3 failed
// May be try?
// Probably a choppy network?
Serial.println("Connection to " + String(host) + " failed. Please check your setup");
// retry??
// execOTA();
}
// Check what is the contentLength and if content type is `application/octet-stream`
Serial.println("contentLength : " + String(contentLength) + ", isValidContentType : " + String(isValidContentType));
// check contentLength and content type
if (contentLength && isValidContentType) {
// Check if there is enough to OTA Update
bool canBegin = Update.begin(contentLength);
// If yes, begin
if (canBegin) {
Serial.println("Begin OTA. This may take 2 - 5 mins to complete. Things might be quite for a while.. Patience!");
// No activity would appear on the Serial monitor
// So be patient. This may take 2 - 5mins to complete
size_t written = Update.writeStream(client);
if (written == contentLength) {
Serial.println("Written : " + String(written) + " successfully");
} else {
Serial.println("Written only : " + String(written) + "/" + String(contentLength) + ". Retry?" );
// retry??
// execOTA();
}
if (Update.end()) {
Serial.println("OTA done!");
if (Update.isFinished()) {
Serial.println("Update successfully completed. Rebooting.");
ESP.restart();
} else {
Serial.println("Update not finished? Something went wrong!");
}
} else {
Serial.println("Error Occurred. Error #: " + String(Update.getError()));
}
} else {
// not enough space to begin OTA
// Understand the partitions and
// space availability
Serial.println("Not enough space to begin OTA");
client.flush();
}
} else {
Serial.println("There was no content in the response");
client.flush();
}
}
void setup() {
//Begin Serial
Serial.begin(115200);
delay(10);
Serial.println("Connecting to " + String(SSID));
// Connect to provided SSID and PSWD
WiFi.begin(SSID, PSWD);
// Wait for connection to establish
while (WiFi.status() != WL_CONNECTED) {
Serial.print("."); // Keep the serial monitor lit!
delay(500);
}
// Connection Succeed
Serial.println("");
Serial.println("Connected to " + String(SSID));
// Execute OTA Update
execOTA();
}
void loop() {
// chill
}
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